One of the nonessential amino acids, found in many proteins, especially collagen. Because the nitrogen atom of its amino group is part of a ring structure (making it a heterocyclic compound), its chemical properties differ from those of the other amino acids in proteins. It is used in biochemical, nutritional, and microbiological research and as a dietary supplement.
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Proline (abbreviated as Pro or P) is an α-amino acid, one of the twenty DNA-encoded amino acids. Its codons are CCU, CCC, CCA, and CCG. It is not an essential amino acid, which means that humans can synthesize it. It is unique among the 20 protein-forming amino acids because the α-amino group is secondary.
Multiple prolines and/or hydroxyprolines in a row can create a polyproline helix, the predominant secondary structure in collagen. The hydroxylation of proline by prolyl hydroxylase (or other additions of electron-withdrawing substituents such as fluorine) increases the conformational stability of collagen significantly. Hence, the hydroxylation of proline is a critical biochemical process for maintaining the connective tissue of higher organisms. Severe diseases such as scurvy can result from defects in this hydroxylation, e.g., mutations in the enzyme prolyl hydroxylase or lack of the necessary ascorbate (vitamin C) cofactor.
Sequences of proline and 2-aminoisobutyric acid (Aib) also form a helical turn structure.
In 2006, scientists at ASU discovered that solutions of TiO2 illuminated with ultraviolet radiation can serve as an extremely cost-effective and accurate protein cleavage catalyst. The TiO2 catalyst preferentially and rapidly cleaves protein at sites where proline is present, while taking much longer to degrade the protein from its endpoints.
From a kinetic standpoint, Cis-trans proline isomerization is a very slow process that can impede the progress of protein folding by trapping one or more proline molecules crucial for folding in the non-native isomer, especially when the native protein requires the cis isomer. This is because proline residues are exclusively synthesized in the ribosome as the trans isomer form. All organisms possess prolyl isomerase enzymes to catalyze this isomerization, and some bacteria have specialized prolyl isomerases associated with the ribosome. However, not all prolines are essential for folding, and protein folding may proceed at a normal rate despite having non-native conformers of many X-Pro peptide bonds.
L-Proline is an osmoprotectant and therefore is used in many pharmaceutical, biotechnological applications.
Proline Supplementation to Parenteral Nutrition Results in Greater Rates of Protein Synthesis in the Muscle, Skin, and Small Intestine in Neonatal Yucatan Miniature Piglets1-3
Jun 01, 2012; Abstract proline and arginine are each indispensable during parenteral feeding due to limited interconversion by an...
Proline is synthesized from glutamate during intragastric infusion but not during intravenous infusion in neonatal piglets
Apr 01, 1996; proline Is Synthesized from Glutamate during Intragastric Infusion but Not during Intravenous Infusion in Neonatal...